The harmful physiological effects of certain constituents contained in tobacco smoke have long been recognized. It is well known, for example, that tobacco smoke contains certain solid tar constituents and health-affecting materials from tobacco smoke by either using various types of tobacco smoke filters attached to the smoking device, or incorporating certain preventive compounds into the tobacco being smoked.
For certain types of tobacco, it is desirable to remove a higher percentage nicotine than tar (as defined by the Federal Trade Commission) to achieve a balance of taste, aroma, undesirable constituents, etc. Throughout the history of cigarette filtration, there has been a desire to selectively remove nicotine from tobacco smoke due to its toxicity. As of the present time, the use of a tobacco smoke filter element placed on the tip of the smoking device is the method or device most commonly used for removing these undesirable components from tobacco smoke. These filters, which normally consist of a bundle of cellulose acetate, convoluted crepe paper, cotton, or combinations of these products formed into a cylindrical plug, are designed to and do remove varying proportions of the liquid-solid particles passing through them, thereby greatly reducing the amount of undesirable materials reaching the smoker's mouth. This liquid-solid particle filtering action is accomplished by a combination of diffusional, impactive, and direct collision of the particles with the filter material. Upon collision the particles are retained in the filter by the surface attraction between the extremely small particles and the relatively large filter material. Thus, filters of this type are capable of removing varying percentages of tar and nicotine from cigarette smoke depending on the amounts of fibrous material compacted into them, their length, their resistance to draw, the surface characteristics of the fibers, and other factors.
Most prior known fibrous filters show no selectivity for the removal of nicotine from the smoke of a cigarette, particularly when the tobacco involved is the conventional type used on domestic cigarettes. This type usually consists of a blend of bright, burley, and Turkish tobaccos with the bright ("flue cured") tobacco constituting the major portion of the blend. Filters of cotton, paper, or cellulose acetate fibers, when attached to such domestic cigarettes, always remove about the same percentage of nicotine from the smoke as they do tar. For example, if one of these filters removes 25% of the tar, it also removes about 25% of the nicotine; if it removes 40% of the tar, it also removes about 40% of the nicotine. Therefore, it can be said that these show no selectivity for removing nicotine over tar.
It has been suggested that one way to make a fibrous filter of cellulose acetate, paper or cotton remove a higher percentage of nicotine than tar from cigarette smoke is to coat the fibers in the filter with acids and particularly with nontoxic, nonvolatile organic acids such as tannic acid, citric acid, glutaric acid and the like. However, such a technique leaves something to be desired from the standpoint of the taste of the filter. Also, in the case of filters of cellulose acetate fibers, the addition of an acid can cause hydrolytic degradation of the fibers on prolonged contact. As a result, acetic acid can be released from the filter giving it an objectionable odor and taste.
U.S. Pat. Nos. 3,417,759 and 3,424,173 describe cigarette filter elements consisting of fibrous filters containing liquid additives (1,4 butanediol and 1,2,4 butanetriol respectively) that selectively remove nicotine from cigarette smoke.
According the the present invention a convenient and effective method has been found by which a tobacco smoke filter can be constructed for the selective removal of nicotine from tobacco smoke. This method consists of coating or otherwise dispersing a particular coating compound on the filtering material from which the tobacco smoke filter element is formed.
Therefore, this invention provides tobacco smoke filters which remove a higher percentage of nicotine than tar from tobacco smoke. Also, this invention provides additives for a tobacco smoke filter which impart to the filter an improved capacity for removing nicotine from tobacco smoke.